The invention relates to a device for guiding a magnetic tape in a recording cassette on two spools which serve alternately as the rewinding and unwinding spools, respectively.
It has been found that in known recording cassettes of this kind the process of rewinding the magnetic tape onto a spool is frequently faulty because the tape is sometimes wound up "in stages", which may give rise to the danger of the tape and spool blocking. The cause of such faulty rewinding normally consists in the fact that the tape is not guided correctly inside the cassette.
On the other hand, when the tape is being unwound from a spool, static electricity is generated which promotes the adhesion of the unwound tape to the outer turn of the tape coil on the spool. This may cause the tape to form a loop inside the cassette, for example on winding back quickly when the braking device does not slow down the unwinding spool and the rewinding spool simultaneously. Unless this loop is made to disappear by the rewinding spool when the recorder is switched over to the "recording/playback position" where the tape is moved forwards at normal speed, a further loop will often form around the sound head or around the pressure roller interacting with the sound head. This then means that the tape has to be drawn out of the cassette, often causing the tape to be destroyed.
In certain types of known cassettes use is made of movable guides for the tape consisting generally of injection-moulded rollers which turn on axle pivots made of stainless steel. These axle pivots are respectively arranged on the appropriate cassette halves in the right and left-hand corners close to the edge in front of the cassette. These rollers are designed to guide the tape as long as possible along a straight path in front of the front or open side of the cassette. Importance attaches to this in the recording or playback position in particular because the slightest deviation or irregularity of the tape along this path may lead to phenomena which are known as "whining" or "howling" and exercise an extremely detrimental influence on tape recording and/or playback.
Known cassettes of this kind, which make use of separating arms to prevent the tape from adhering to the coil under the action of the static electricity, therefore have a total number of six parts to exercise the guiding function for the tape, i.e. one arm, one guide roller and one separate swivel axis for the arm on each side of the cassette.
In known guiding devices for the magnetic tapes in cassettes, another disadvantageous factor is that it is extremely difficult to thread the tape into the guiding device and take it out again.
The object of the invention is therefore to avoid these disadvantages and to provide a device of the kind named at the beginning which can be manufactured very simply and easily and circumvents the constructional costs peculiar to the known guiding devices. The device to be provided is furthermore intended to ensure that the tape is correctly guided in the cassette with a minimum of friction, this being of importance when the cassette is employed for audio-visual recorders or magnetic memories that are required to work precisely. Finally, the threading of the tape into, and removal from, this guiding device are also designed to be carried out with great ease and facility thanks to the design of the device so that the threading and removal processes can be done in one step, respectively.